Heat responsive switch



Oct. 26, 1948.

A. WARSHER HEAT RESPONSIVE SWITCH Filed July 7, 1944 M 1 Rm m m W m W Mn l w A 2 "QM Patented Oct. 26, 1948 2,452,511 HEAT RESPONSIVE swrron Adolph Warsher, Maywood, N. J assignor to Maxwell M. Bllofsky, Newark, N. J.

Application July 7, 1944, Serial No. 543,939

. 4 Claims. (Cl. ZOO-113.5)

It is among the objects of the invention to provide a glow discharge switch 01 simple and relatively inexpensive construction, which shall be applicable in all relations where it' is desired automatically and sensitively to control a circuit in differentiated manner, depending upon the magnitude of heat evolved by the glow discharge gap, and in which the operation and control is effected with complete safety, even though the switch be used in environment where explosive gas mixtures may be encountered.

The invention has an important application to thermionic lamp starters oi the glow discharge type and in that application further and more specialized objects are to provide a device of the above type which shall readily be replaceable for the conventional glow discharge starter, and which shall in addition to the primary lamp start in function, perform the further function oi promptly and automatically inhibiting the intermittent flashing of a lamp that has become defective, as for instance, by loss of emissive coating from its electrodes and which shall do so without the drastic curtailment in life incurred with the use of conventional glow discharge switches under such intermittent flashing and yet, under normal operating conditions, with a perfect lamp, shall not add in the least to the wattage consumed in lamp ope-ration.

Another object is to provide a device or" the 1 above type, which despite its added intermittent iiash inhibiting utility, shall be substantially as simple, as compact and inexpensive in construction as the conventional glOW discharge switch used for thermionic lamp starters and that lacks such utility, and which shall require no manual resetting operation to resume its various functions after the lamp circuit has been interrupted.

Generally stated the invention involves includin in the hermeti -ally sealed envelope for the thermally resp e strip used in the convenstarter for thermionic devices, ch are thermally responsive and which carry e normally spaced coacting discharge gap sh eircuiting contacts, one of said electrodes being more sluggish than the other and being arranged so that under the prolonged heating of the glOW discharge incurred with a defective lamp for instance, it will deflect its contact out of the path of movement of the companion contact, so that the discharge is maintained across the gap and the latter remains open as long as the switch remains in circuit.

In the accompanying drawings in which is shown one of various possible embodiments of the several features of the invention,

1 is a plan view of the glow discharge switch,

Fig. 2 is a sectional View taken on line 2-2 of Fig. 1, I

Fig. 3 is a sectional detailed view taken on line 3-3 of Fig. 1, and

Fig. 4 is a circuit diagram showing the application of the glow discharge switch as a starter for a thermionic lamp,

' Referring to Figs. 1 to 3 of the drawings, the switch comprises a hermetically sealed envelope Ill, desirably of glass, exhausted of air through tube ii and charged with noble gas such as neon under very low pressure. Through the stem [2 of the envelope extend the two terminals i3 and i l. Upon the post it of terminal l3 and post l6 of terminal M respectively, are afiixed the two electrodes ll and it which carry respectively contacts i9 and 2t normally spaced from each other.

According to the invention, the electrodes H and iii are both thermally responsive, for which purpose, each of them is preferably of bi-metal. Electrode it is relatively sluggish in its heat response, so that in the lamp starter application for instance, its contact during operation with a perfect lamp remains to all intents and purposes 1 xed and undisplaced and the more sensitive heat responsive electrode ill will function in the conventional manner to short circuit the glow dis charge between the electrodes, which to that end, are coated. with suitable electron emissive material.

In the specific embodiment shown, the more sensitive bi-metal electrode ll is a U-shaped strip, one leg ill of which is afdxed upon and rises from post it, the extremity of the free downturned leg 22 thereof carrying contact ill in the form of a rod that is soldered or welded along the lower edge thereof. The more sluggish bi-metal electrode i8 is also iJ-shaped, with one leg 23 thereof affixed upon and rising from post it. The width of the'f-ree downturned leg 2d of electrode it extends at an angle, and preferably as shown, at a right angle to the width of the corresponding leg 22 of the other electrode, and. across and slightly spaced from the edge of the latter, as appears most clearly from Fig. l. The contact 2Q on electrode i8 is in the form of a'rod soldered or welded near and along the lower edge of the free leg 2d thereof. Contact rod Ell has its effective contact portion directed outward as leg 20' at right angles to leg 24 and parallel to and in the path of the contact rod 89 on electrode H. The

bi.-meta1 on the electrode l8 has the element or greater co-efflcient of expansion on the convex or outer side thereof, whilein the case of the more sensitive electrode I1 the metal of greater coefficient of expansion is on the concave or inner face thereof, so that with rise in temperature, the free leg will approach the fixed leg of electrode i8 while in the case of electrode H, the free leg will recede from the fixed le with temperature rise.

In Fig. 4 is shown the circuit diagram of an important application of the glow discharge switch in one of its various uses, i. e. for the starting of a conventional thermionic lamp L, the electrode filaments 3| and 32 of which are covered with an electron emissive coating of barium or strontium oxide.

The glow switch starter S bridged by the usual condenser 29 is in the starting circuit 30, which connects lamp electrodes 3! and 32 in series, for electrically heating the same. An iron core ballast coil 33 is in the line and the lowering of the power factor of the system due to its operation is compensated for by condenser 34; across the line, all in accordance with conventional practice.

In the operation of the conventional glow switch starter, the applied voltage is at the outset sufilcient to cause the glow discharge in the gap, but is insufiicient to cause arcing of the lamp L. Under the heat of the glow discharge, the bimetal strip i7 deflects to cause its contact 89 to engage contact 20' and to store energy in ballast coil 33. The glow discharge being thus interrupted bi-metal strip ll cools and contacts away from contact 20'. As a result of this opening of the starter circuit, the impulse from the ballast coil 33 tends to start the arc in the lamp L across its now heated electrodes 3i and 32 and the starting cycle set forth is resumed until the arc in the lamp L has actually been struck. Since such arc, when once maintained, requires voltage less than that required to initiate the glow discharge in the starter switch S the latter remains out of action.

Should the lamp be or become defective, as for instance, due to the loss of emissive material from one or both of its electrodes, so that the lamp will falter instead of maintaining its arc, the conventional glow switch starter (devoid of the present improvement) would repeat the cycle above set forth and cause the lamp intermittently to flash on and off, to the annoyance of the user and with greatly curtailed life of the glow discharge switch.

With the glow discharge switch of the present invention, should the glow discharge be prolonged or maintained for an abnormal length of time, due to slow starting or restarting of a defective lamp, the more sluggish bi-metal electrode strip 18 which in normal operation will not move, will be deflected, for its leg 2 to move inward in the direction of the arrow in Figs. 1 and 3, toward the support post i6. In this operation, the contact lengthw 20' is displaced in a direction at right angles to the outward movement of contact I9 on the electrode strip ll, so that it clears the edge of said strip IT and is outof the path of movement of the latter, so that short-circuiting of the discharge gap is precluded. Accordingly, the discharge gap will be maintained between the two spaced electrodes i! and i8, and the heat generated in such gap maintains both of said electrodes in their deflected position, as long as the glow discharge switch remains in circuit, whereby the intermittent flashing of such det ctive lamp and the excessive wear and tear to which a conventional glow discharge switch would be subjected under such conditions are obviated.

When the circuit to the glow discharge switch is reopened (as by opening main switch 35) the parts cool, the more sensitive electrode strip I? promptly returning to the normal position, followed by return of the more sluggish electrode strip I8, back to the normal position, best shown in Fig. 1. Accordingly, the device automatically returns to its normal position in readiness to perform its starting as well as its automatic cut-out safety or protective function and this without the need for any manual resetting operation.

For convenience, the electrode H by the movement of which the discharge gap may be short circuited is called the switching electrode, and the electrode i8 by the movement of which such short-circuiting is precluded, is called the safety electrode.

The glow switch starter is a unit of small bulk, in fact, in its lamp starter form, it is of bulk so small that there is no need for alteration in the thermionic lamp fixtures now in use, that are designed for conventional glow switch starters, to enable replacement of the'latter by the improved glow switch starter of the present invention. The invention may in fact utilize the envelope and the switching electrode of the conventional glow discharge switch and the only change structurally from such conventional switch is the substitution of the second bi-metal or safety electrode disclosed for the fixed contact strip.

In operation, the glow discharge switch of the present invention functions to control a perfect lamp in precisely the same way as does a glow discharge switch of conventional type. The presence of the added safety feature does not add in the least to the power consumption, as long as the controlled lamp is without defect,

The glow discharge switch is of course useful as an automatic control switch in a wide variety of applications, in fact, in any relation in which in switching in the circuit connections is automatically to be effected in response to heat.

By the term glow discharge switch as used in the claims is meant a unit of the general character described, which is charged with a noble gas or mixture of noble gases at pressure such, as to develop a glow discharge across its electrodes at voltage controlling a step in the operation of the system or device with which it is used.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it

is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A glow discharge switch comprising a hermetically sealed envelope, a pair of thermally responsive electrodes "therein determining a glow discharge gap therebetween, said electrodes being located so that the deflection path of one is at an angle to the deflection paths of the other, one of said electrodes being responsive to heat evolved in said gap to short circuit the latter, the other electrode being responsive to prolonged heating for deflection laterally out of the path of flection of said first electrode whereby, after short circuiting electrode will be rendered inoperative to short circuit said gap and the latter will be maintained until the circuit to said glow discharge switch is interrupted.

2. A glow discharge switch comprising a hermetically sealed envelope, a pair of thermally responsive electrodes therein forming a glow discharge gap therebetween, said electrodes being located so that the deflection path of one is at an angle to the deflection path of the other, each of said electrodes carrying a contact, said con.

tacts being normally spaced but correlated for engagement to short circuit said glow discharge gap upon deflection of one of said electrodes by the heat involved in said envelope, the other of said electrodes being relatively sluggish in its thermal response whereby, after prolonged heating of said second electrode, the latter will be deflected laterally out of the path of movement of said first electrode, thereby rendering said first electrode inoperative to short circuit said gap and the latter will be maintained until the circuit to said glow discharge switch is'interrupted.

3. A glow discharge switch, comprising 9. hermetically sealed envelope, electrodes therein, spaced for glow discharge therebetween, said electrodes comprising a U-shaped bi-metal switching electrode supported by one leg thereof and having a contactat the end of the other leg thereof, a U-shaped bi-metal safety electrode more sluggish in its heat response, supported byone leg thereof and having the width thereof arranged in a plane at an angle to that of the switching electrode, a contact carried by the end of the other leg of the said safety electrode and in the path of movement of the contact of the switching electrode, for engagernent thereby whereby under normal condi-.

tions of operation said switching electrode will short circuit said glow discharge gap and after prolonged heating of said safety electrode, the latter will be deflected laterally at an angle to the movement of the contact on the switching electrode and out of the path of the latter to preclude short circuiting of said glow discharge gap as long as the glow discharge switch remains in the circuit.

4. The combination recited in claim 3 in which the widths of the free legs of the bi-metal electrodes extend in planes at right angles to each other, in which the contact on the safety electrode protrudes at right angles to the leg thereof and parallel to the contact on the switching electrode and in which, under continued heat evolution, the leg of the safety electrode moves toward the supported leg thereof.

ADOLPH WARSHER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date Thomas Jan. 5, 1932 Weirich May 11, 1937 Cook Feb. 24, 1942 Bensin Oct. 19, 1943 Pennybacker et al. July 25, 1944 

